With reference to FIGS. 1-4, we shall explain a valve assembly for mixing warm and cold tap water. It has a valve housing 1 having a discharge passage 2 and a recess 5. In the recess 5 are mounted, from below, a valve seat 6, a valve body 7 and a seal ring 8 one upon another. A lever holder 9 is rotatably fitted in the top part of the valve housing 1. It carries a lever 10 for actuating the valve body 7.
The valve seat 6 is fixedly mounted on a base 12 by engagement with protrusions 11 on the base 12 and is formed with a pair of elongated inlet passages 13, 14 in an opposed arrangement (FIG. 2). The passages 13, 14 can be brought into communication with circular inlet passages 3, 4 formed through the base 12.
The valve body 7 is disk-shaped and has a diameter smaller than the inner diameter of the valve housing recess 5. It is slidable relative to the valve seat 6 and the seal ring 8. Between the valve body 7 and the valve seat 6 are provided flow passages 15 formed by two cutouts so as to communicate with the discharge passage 2.
Between the valve seat 6 and the base 12 is mounted a rubber packing. 16. Also, a rubber O-ring 19 is fitted on the top surface of the seal ring 8. By the elasticity of the packing 16 and the O-ring 19, a liquid-tight seal is provided between the base 12 and the valve seat 6, between the valve seat 6 and the valve body 7 and between the valve body 7 and the seal ring 8.
The valve body 7 and the lever 10 are operatively coupled together through a link rod 17 supported on the lever holder 9 by means of a pin 18. By moving up and down and turning the lever 10, the valve body 7 can be moved to a desired position to open the faucet to obtain selectively hot water, cold water or a mixture thereof and to close the faucet.
In the state shown in FIGS. 1 and 2, the valve body 7 is moved to the rightmost end, so that flow passages 15 communicates with neither of the inlet passages 13, 14. In the state of FIG. 3, the valve body 7 is in such a position that the flow passages 15 communicate with one of the inlet passages 13, i.e. the position in which only hot water or cold water is discharged. FIG. 4 shows a position of the valve body 7 in which the flow passages 15 communicate with both of the inlet passages 13, 14, so that a mixture of hot water and cold water is discharged.
In Unexamined Japanese Patent Publication 63-36765, it is disclosed to form one of the valve body 7 and the valve seat 6 of a ceramic material and the other from a resin having self-lubricity such as a fluororesin or a high-molecular weight polyethylene, or a resin containing a filler such as molybdenum disulfide or carbon to improve its lubricity.
But the conventional valve body made of a self-lubricating resin is low in creep resistance. Even if a fibrous filler is added to the material of such a valve body, it cannot sufficiently reinforce the valve body because the wettability between the filler and the resin is low. Such a valve body can withstand only a low water pressure. If it is desired to improve the lubricity of a valve body made of a non-self-lubricating resin that exhibits high reinforcing effect, a large amount of self-lubricating filler has to be added thereto. Addition of such a large amount of filler will lead to marked reduction in shock strength and creep resistance. Such a valve body tends to develop cracks or can have poor water tightness.
Unexamined Japanese Patent Publication 2-190677 discloses a resin composition that shows somewhat improved creep resistance and lubricity. It comprises 25-80% by weight of a polyphenylene sulfide resin and 20-75% by weight of carbon fiber having an average fiber diameter of 8 .mu.m with inorganic powdery fillers such as natural mica added.
But valve bodies made mainly of polyphenylene sulfide have a problem in that even a very slight inaccuracy in flatness of the sliding contact surfaces between such valve bodies can make difficult liquid-tight contact between the valve bodies. Thus, any increase in the surface roughness due to wear or any inaccuracy in flatness due to swelling, creeping or mechanical or thermal shock can lead to water leakage.
Another major cause of water leakage in the valve device having a valve body or a valve seat made of such a synthetic resin is damage on the sliding contact surfaces of the valve seat and the valve body by foreign matter that has intruded into between the contact surfaces during use, thus decreasing the water cut-off property.
It is therefore an object of this invention to provide a valve assembly which is free of the above problems, which has a valve body that has a sliding contact surface whose surface roughness never increases while in use, which is less likely to be damaged by foreign objects and which has excellent mechanical properties such as creep resistance, thereby showing high water cut-off ability and lever controllability even after long use.